1. Field of the Invention
The present invention relates to a valved discharge mechanism of a fluid displacement apparatus, and more particularly, to a valued discharge mechanism of a refrigerant compressor used in an automotive air conditioning system.
2. Description of the Prior Art
Valved discharge mechanisms of refrigerant compressors are well known in the prior art. For example, FIG. 1 depicts a suction port mechanism used in a refrigerant compressor according to the prior art. As disclosed therein, the refrigerant compressor includes a compressor housing defining a compression chamber in which successive strokes of intake, compressing, and discharge of a refrigerant gas are repeatedly performed. Further, the compressor includes valve plate 25, which partitions the compression chamber and the discharge chamber, and a discharge valve assembly, which is mounted on an end surface of valve plate 25. Valve plate 25 has a discharge hole 252 extending therethrough to allow communication of the compression chamber with the discharge chamber. The discharge valve assembly includes discharge valve 81 and valve retainer 80, which are secured to end surface 25a of valve plate 25 by bolt 82. Discharge reed valve 81, which is made of an elastic material, regulates the flows of the refrigerant gas and sealingly engages end surface 25a of valve plate 25 when the operation of the compressor is stopped.
Valve retainer 80 limits the bending movement of discharge reed valve 81 in the direction in which the refrigerant gas exits the compression chamber and enters the discharge chamber through discharge hole 252. Discharge reed valve 81 has an elastic modulus which keeps discharge hole 252 closed until the pressure in the compression chamber reaches a predetermined value. Discharge reed valve 81 strikes valve retainer 80 when it opens, and strikes end surface 25a of valve plate 25 when it closes. This striking generates vibration and noises during operation of the compressor. Vibration caused by reed valve 81 striking end surface 25a of valve plate 25 is readily transmitted to the compressor housing.
One solution attempted by the assignor of the present application is depicted in FIG. 2. Though not prior art, this attempt is illustrative of progress in this area. There, valve plate 25 includes recessed portion 350 formed so that its depth increases with distance from point B, which is located on valve plate 25 and is spaced a distance L from bolt 82. Recessed portion 350 includes curved surface 351 surrounding discharge hole 352. When discharge reed valve 81 is in its closed position, it sealingly engages curved surface 351. Curved surface 351 has a radius of curvature R1, which defines the closing deformation of discharge reed valve 81.
Further, valve retainer 80 includes curved surface 80a having radius of curvature R2, which defines the opening deformation of discharge reed valve 81. Radius of curvature R1 is designed to be equal to or less than radius of curvature R2 so that when discharge reed valve 81 closes, its elastic restoring force will not cause it to strike end surface 25a of valve plate 25 with significant force. Curved surface 80a of valve retainer 80 begins curving away from valve plate 25 at point A, which is also spaced a distance L from bolt 82.
The impact force with which discharge reed valve 81 strikes curved surface 351 of valve plate 25 in FIG. 2 is smaller than that which discharge reed valve 81 strikes end surface 25a of valve plate 25 in FIG. 1. While noise and vibration caused by discharge reed valve 81 are reduced in comparison with the arrangement of FIG. 1, the closing of discharge reed valve is delayed in comparison with FIG. 1 due to recessed portion 350. As a result, volumetric efficiency of the compressor is decreased.